def time2str(num):
    d = int(num/3600/24)
    h = int((num-d*3600*24)/3600)
    m = int((num-d*3600*24-h*3600)/60)
    s = int(num - d*3600*24-h*3600-m*60)
    if d == 0 and h == 0 and m == 0:
        return str(s)+'秒'
    elif d == 0 and h == 0:
        return str(m)+'分'+str(s)+'秒'
    elif d == 0 :
        return str(h)+'时'+str(m)+'分'+str(s)+'秒'
    else:
        return str(d)+'天'+str(h)+'时'+str(m)+'分'+str(s)+'秒'